pygsti.processors.processorspec

Defines the QubitProcessorSpec class and supporting functionality.

Module Contents

Classes

ProcessorSpec

The API presented by a quantum processor, and possible classical control processors.

QubitProcessorSpec

The device specification for a one or more qubit quantum computer.

class pygsti.processors.processorspec.ProcessorSpec

Bases: pygsti.baseobjs.nicelyserializable.NicelySerializable

The API presented by a quantum processor, and possible classical control processors.

Operation names and ideal actions (e.g. gate names and their unitaries) are stored in a processor specification, as is the availability of the different operations and overall proccesor geometry. Processor specifications do not include any information about how operations are parameterized or can be adjusted (at least not yet).

class pygsti.processors.processorspec.QubitProcessorSpec(num_qubits, gate_names, nonstd_gate_unitaries=None, availability=None, geometry=None, qubit_labels=None, nonstd_gate_symplecticreps=None, aux_info=None)

Bases: ProcessorSpec

The device specification for a one or more qubit quantum computer.

This is objected is geared towards multi-qubit devices; many of the contained structures are superfluous in the case of a single qubit.

Parameters
  • num_qubits (int) – The number of qubits in the device.

  • gate_names (list of strings) –

    The names of gates in the device. This may include standard gate names known by pyGSTi (see below) or names which appear in the nonstd_gate_unitaries argument. The set of standard gate names includes, but is not limited to:

    • ’Gi’ : the 1Q idle operation

    • ’Gx’,’Gy’,’Gz’ : 1-qubit pi/2 rotations

    • ’Gxpi’,’Gypi’,’Gzpi’ : 1-qubit pi rotations

    • ’Gh’ : Hadamard

    • ’Gp’ : phase or S-gate (i.e., ((1,0),(0,i)))

    • ’Gcphase’,’Gcnot’,’Gswap’ : standard 2-qubit gates

    Alternative names can be used for all or any of these gates, but then they must be explicitly defined in the nonstd_gate_unitaries dictionary. Including any standard names in nonstd_gate_unitaries overrides the default (builtin) unitary with the one supplied.

  • nonstd_gate_unitaries (dictionary of numpy arrays) – A dictionary with keys that are gate names (strings) and values that are numpy arrays specifying quantum gates in terms of unitary matrices. This is an additional “lookup” database of unitaries - to add a gate to this QubitProcessorSpec its names still needs to appear in the gate_names list. This dictionary’s values specify additional (target) native gates that can be implemented in the device as unitaries acting on ordinary pure-state-vectors, in the standard computationl basis. These unitaries need not, and often should not, be unitaries acting on all of the qubits. E.g., a CNOT gate is specified by a key that is the desired name for CNOT, and a value that is the standard 4 x 4 complex matrix for CNOT. All gate names must start with ‘G’. As an advanced behavior, a unitary-matrix-returning function which takes a single argument - a tuple of label arguments - may be given instead of a single matrix to create an operation factory which allows continuously-parameterized gates. This function must also return an empty/dummy unitary when None is given as it’s argument.

  • availability (dict, optional) – A dictionary whose keys are some subset of the keys (which are gate names) nonstd_gate_unitaries and the strings (which are gate names) in gate_names and whose values are lists of qubit-label-tuples. Each qubit-label-tuple must have length equal to the number of qubits the corresponding gate acts upon, and causes that gate to be available to act on the specified qubits. Instead of a list of tuples, values of availability may take the special values “all-permutations” and “all-combinations”, which as their names imply, equate to all possible permutations and combinations of the appropriate number of qubit labels (deterined by the gate’s dimension). If a gate name is not present in availability, the default is “all-permutations”. So, the availability of a gate only needs to be specified when it cannot act in every valid way on the qubits (e.g., the device does not have all-to-all connectivity).

  • geometry ({"line","ring","grid","torus"} or QubitGraph, optional) – The type of connectivity among the qubits, specifying a graph used to define neighbor relationships. Alternatively, a QubitGraph object with qubit_labels as the node labels may be passed directly. This argument is only used as a convenient way of specifying gate availability (edge connections are used for gates whose availability is unspecified by availability or whose value there is “all-edges”).

  • qubit_labels (list or tuple, optional) – The labels (integers or strings) of the qubits. If None, then the integers starting with zero are used.

  • nonstd_gate_symplecticreps (dict, optional) – A dictionary similar to nonstd_gate_unitaries that supplies, instead of a unitary matrix, the symplectic representation of a Clifford operations, given as a 2-tuple of numpy arrays.

  • aux_info (dict, optional) – Any additional information that should be attached to this processor spec.

_to_nice_serialization(self)
classmethod _from_nice_serialization(cls, state)
property num_qubits(self)

The number of qubits.

property primitive_op_labels(self)

All the primitive operation labels derived from the gate names and availabilities

gate_num_qubits(self, gate_name)

The number of qubits that a given gate acts upon.

Parameters

gate_name (str) – The name of the gate.

Returns

int

resolved_availability(self, gate_name, tuple_or_function='auto')

The availability of a given gate, resolved as either a tuple of sslbl-tuples or a function.

This function does more than just access the availability attribute, as this may hold special values like “all-edges”. It takes the value of self.availability[gate_name] and resolves and converts it into the desired format: either a tuple of state-space labels or a function with a single state-space-labels-tuple argument.

Parameters
  • gate_name (str) – The gate name to get the availability of.

  • tuple_or_function ({'tuple', 'function', 'auto'}) – The type of object to return. ‘tuple’ means a tuple of state space label tuples, e.g. ((0,1), (1,2)). ‘function’ means a function that takes a single state space label tuple argument and returns True or False to indicate whether the gate is available on the given target labels. If ‘auto’ is given, then either a tuple or function is returned - whichever is more computationally convenient.

Returns

tuple or function

_resolve_availability(self, avail_entry, gate_nqubits, tuple_or_function='auto')
is_available(self, gate_label)

Check whether a gate at a given location is available.

Parameters

gate_label (Label) – The gate name and target labels to check availability of.

Returns

bool

available_gatenames(self, sslbls)

List all the gate names that are available within a set of state space labels.

This function finds all the gate names that are available for at least a subset of sslbls.

Parameters

sslbls (tuple) – The state space labels to find availability within.

Returns

tuple of strings – A tuple of gate names (strings).

available_gatelabels(self, gate_name, sslbls)

List all the gate labels that are available for gate_name on at least a subset of sslbls.

Parameters
  • gate_name (str) – The gate name.

  • sslbls (tuple) – The state space labels to find availability within.

Returns

tuple of Labels – The available gate labels (all with name gate_name).

force_recompute_gate_relationships(self)

Invalidates LRU caches for all compute_* methods of this object, forcing them to recompute their values.

The compute_* methods of this processor spec compute various relationships and properties of its gates. These routines can be computationally intensive, and so their values are cached for performance. If the gates of a processor spec changes and its compute_* methods are used, force_recompute_gate_relationships should be called.

compute_clifford_symplectic_reps(self, gatename_filter=None)

Constructs a dictionary of the symplectic representations for all the Clifford gates in this processor spec.

Parameters

gatename_filter (iterable, optional) – A list, tuple, or set of gate names whose symplectic representations should be returned (if they exist).

Returns

dict – keys are gate names, values are (symplectic_matrix, phase_vector) tuples.

compute_one_qubit_gate_relations(self)

Computes the basic pair-wise relationships relationships between the gates.

1. It multiplies all possible combinations of two 1-qubit gates together, from the full model available to in this device. If the two gates multiple to another 1-qubit gate from this set of gates this is recorded in the dictionary self.oneQgate_relations. If the 1-qubit gate with name name1 followed by the 1-qubit gate with name name2 multiple (up to phase) to the gate with name3, then self.oneQgate_relations[name1,`name2`] = name3.

2. If the inverse of any 1-qubit gate is contained in the model, this is recorded in the dictionary self.gate_inverse.

Returns

  • gate_relations (dict) – Keys are (gatename1, gatename2) and values are either the gate name of the product of the two gates or None, signifying the identity.

  • gate_inverses (dict) – Keys and values are gate names, mapping a gate name to its inverse gate (if one exists).

compute_multiqubit_inversion_relations(self)

Computes the inverses of multi-qubit (>1 qubit) gates.

Finds whether any of the multi-qubit gates in this device also have their inverse in the model. That is, if the unitaries for the multi-qubit gate with name name1 followed by the multi-qubit gate (of the same dimension) with name name2 multiple (up to phase) to the identity, then gate_inverse[name1] = name2 and gate_inverse[name2] = name1

1-qubit gates are not computed by this method, as they are be computed by the method :method:`compute_one_qubit_gate_relations`.

Returns

gate_inverse (dict) – Keys and values are gate names, mapping a gate name to its inverse gate (if one exists).

compute_clifford_ops_on_qubits(self)

Constructs a dictionary mapping tuples of state space labels to the clifford operations available on them.

Returns

dict – A dictionary with keys that are state space label tuples and values that are lists of gate labels, giving the available Clifford gates on those target labels.

compute_ops_on_qubits(self)

Constructs a dictionary mapping tuples of state space labels to the operations available on them.

Returns

dict – A dictionary with keys that are state space label tuples and values that are lists of gate labels, giving the available gates on those target labels.

compute_clifford_2Q_connectivity(self)

Constructs a graph encoding the connectivity between qubits via 2-qubit Clifford gates.

Returns

QubitGraph – A graph with nodes equal to the qubit labels and edges present whenever there is a 2-qubit Clifford gate between the vertex qubits.

compute_2Q_connectivity(self)

Constructs a graph encoding the connectivity between qubits via 2-qubit gates.

Returns

QubitGraph – A graph with nodes equal to the qubit labels and edges present whenever there is a 2-qubit gate between the vertex qubits.

subset(self, gate_names_to_include='all', qubit_labels_to_keep='all')

Construct a smaller processor specification by keeping only a select set of gates from this processor spec.

Parameters

gate_names_to_include (list or tuple or set) – The gate names that should be included in the returned processor spec.

Returns

QubitProcessorSpec

map_qubit_labels(self, mapper)

Creates a new QubitProcessorSpec whose qubit labels are updated according to the mapping function mapper.

Parameters

mapper (dict or function) – A dictionary whose keys are the existing self.qubit_labels values and whose value are the new labels, or a function which takes a single (existing qubit-label) argument and returns a new qubit label.

Returns

QubitProcessorSpec

property idle_gate_names(self)

The gate names that correspond to idle operations.

property global_idle_gate_name(self)

The (first) gate name that corresponds to a global idle operation.

property global_idle_layer_label(self)

Similar to global_idle_gate_name but include the appropriate sslbls (either None or all the qubits)